What solar panel costs qualify for capital allowances?
HMRC classifies solar PV system components as plant and machinery (P&M) qualifying for AIA and FYA. Qualifying costs include: PV panels, inverters, string combiners and protection equipment, mounting systems (ballasted or mechanically fixed), DC cabling and AC cabling from inverter to switchboard, monitoring and metering equipment, battery storage systems, and associated switchgear. Costs that do not qualify as P&M: structural reinforcement (qualifies as integral features at 6% WDA), scaffolding and access equipment included in the contract (treat as preliminaries in the cost split), and planning fees.
100% Annual Investment Allowance (AIA)
Solar PV qualifies as plant and machinery for UK businesses. 100% AIA applies to the first £1m of qualifying P&M capex per company per tax year. For a £900k install, year-one tax shield is £225k (at 25% corporation tax). Effective net cost: £675k. Net cash payback: 3.1 years. AIA was indefinitely extended at the £1m level in Spring 2024 Budget. Group companies share a single £1m AIA — important for property investors or manufacturers with multiple entities.
50% First Year Allowance (FYA)
Above the £1m AIA cap, residual qualifying P&M capex falls into the 50% First Year Allowance for special-rate plant — subject to current legislation. Half the residual capex is expensed in year one; remainder depreciates at 6% writing down allowance. For a £2m install, year-one tax shield: £225k AIA + £125k FYA = £350k. FYA is available to companies within the charge to UK corporation tax — sole traders and partnerships cannot use FYA but can use the equivalent annual investment allowance.
Freeport Enhanced Capital Allowance (ECA)
Within UK Freeports (Felixstowe & Harwich, Liverpool, Plymouth, Teesside, Solent, Thames, Humber, East Midlands Airport), 100% ECA on plant and machinery within the designated Freeport tax site, on top of standard AIA. For a £2m project in a Freeport zone, ECA delivers approximately £500k of year-one tax shield (at 25% corporation tax) — bringing net cash payback under 4 years. Freeport ECA is available until at least 30 September 2031 under current legislation.
How to claim capital allowances on solar panels
Capital allowances on solar panels are claimed through your company tax return (CT600) in the capital allowances section (boxes 785-802). Step 1: obtain a capital allowances cost split from your installer breaking out qualifying P&M (panels, inverters, cables, mounting, monitoring) vs integral features (structural reinforcement) vs excluded costs. Step 2: confirm the company tax year in which the asset is "brought into use" — this is the date of commissioning and final DNO energisation, not contract signature or practical completion. Step 3: enter qualifying P&M expenditure in box 785 (AIA) up to the £1m cap, and in box 792 (FYA) for remainder. Step 4: ensure group AIA allocation is correctly split if the company is part of a group. We provide a compliant cost split document as a standard project deliverable.
Tax planning at scale
For multi-site rollouts, sequencing capex across tax years can preserve AIA across multiple buildings. A £5m portfolio rollout split across 5 tax years preserves £1m AIA per year, maximising year-one tax shield per project. Group company structures may need AIA allocation agreements. Tax planning matters at scale — we recommend involving your tax advisor at the proposal stage for projects above £2m.
Common questions
Can I claim capital allowances on solar panels?
Yes. HMRC classifies solar PV panels, inverters, mounting systems, cabling, monitoring, and battery storage as plant and machinery — qualifying for 100% Annual Investment Allowance (first £1m per tax year) and 50% First Year Allowance above £1m. We provide a compliant cost split document as a standard project deliverable for your tax return.
What's the year-one tax shield on a typical install?
For £900k install: £225k year-one tax shield (£900k AIA × 25% corporation tax). Effective net cost: £675k. Net cash payback: 3.1 years. For a £2m install: £225k AIA + £125k FYA = £350k year-one tax shield.
How does Freeport ECA stack with AIA?
Freeport ECA provides 100% Enhanced Capital Allowance on plant and machinery within designated Freeport tax sites, on top of standard 100% AIA. For £2m project, total year-one tax shield approaches £500k (at 25% corporation tax) — bringing net cash payback under 4 years. Available to 30 September 2031.
When is a solar installation "brought into use" for capital allowances?
The asset is "brought into use" on the date it is commissioned and energised — when the final DNO G99 energisation takes place and the system generates its first export to grid. This is the key date for determining which tax year the capital allowances apply in. Contract signature and practical completion are not the relevant dates.